<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      function getMoney() {
        let num1 = +prompt('输入银行卡余额')
        let num2 = +prompt('输入当月食宿消费金额')
        let num3 = +prompt('输入当月生活消费金额')
        let surplus = num1 - num2 - num3
        return surplus
      }
      let res = getMoney()
      alert(`银行卡剩余金额：${res}`);
    </script>
  </body>
</html>
